def p(n):
    for i in range(2,n):
        if n%i==0:
            return False
    return True
x=[]
b=['zero','one','two','three','four','five','six','seven','eight','nine']
a=input()
a=a.split()
if len(a)<3 or a[0] not in b or a[1] not in b or a[2] not in b:
    print("Wrong input")
else:
    for i in a:
        if i=='one':
            x.append('1')
        if i=='two':
            x.append('2')
        if i=='three':
            x.append('3')
        if i=='four':
            x.append('4')
        if i=='five':
            x.append('5')
        if i=='six':
            x.append('6')
        if i=='seven':
            x.append('7')
        if i=='eight':
            x.append('8')
        if i=='nine':
            x.append('9')
    s=''.join(x)
    prost=[]
    for i in range(2,1500):
        if p(i):
            prost.append(i)
    mn=10000
    k=0
    for i in prost:
        if abs(i-int(s))<mn:
            mn=abs(i-int(s))
            k=i
    print(k)
        
    
